Electronic sphygmomanometer and blood pressure measuring method

ABSTRACT

An electronic sphygmomanometer includes a central processing unit (CPU) that calculates a blood pressure calculation parameter by executing a predetermined calculation using a constant set in advance with respect to a change in a pressure pulse wave amplitude indicating a volume change of an artery at the time of blood pressure measurement. The CPU separately acquires measurement state related information related to a state of a user and/or a state of the cuff at the time of blood pressure measurement. When the measurement state related information is acquired, the CPU corrects the blood pressure calculation parameter by correcting the constant based on the measurement state related information.

TECHNICAL FIELD

The present invention relates to an electronic sphygmomanometerincluding a cuff to be attached to a blood pressure measurement site anda blood pressure calculation unit for calculating a blood pressure valuefrom a cuff pressure, and a blood pressure measuring method using thesame.

BACKGROUND ART

A blood pressure is one type of index for analyzing a circulatorydisease. Performing risk analysis based on the blood pressure iseffective in preventing cardiovascular related disease such as apoplexy,cardiac arrest, and cardiac infarction. Conventionally, a diagnosis forperforming the risk analysis is made from the blood pressure (occasionalblood pressure) measured in medical institutions at the time of hospitalvisits and checkups. However, it is recognized from recent research thatthe blood pressure (home blood pressure) measured at home is more usefulin diagnosing the circulatory disease than the occasional bloodpressure. Accompanied therewith, the sphygmomanometer used at home isbeing widely used.

Most of the electronic sphygmomanometers currently being widely used usea blood pressure calculation algorithm of an oscillometric method. Inthe oscillometric method, a cuff is wrapped around a measurement sitesuch as an upper arm and pressurized up to a predetermined pressure, andthen depressurized gradually or in a step-wise manner. The oscillometricmethod is a method of detecting a change in arterial volume that occursin the middle of depressurization as a pressure change (pressure pulsewave amplitude) superimposed on the cuff pressure, and applying apredetermined algorithm on the change in pressure pulse wave amplitudeto determine the systolic blood pressure and the diastolic bloodpressure. Generally, a point where the pressure pulse wave amplitudesuddenly becomes large obtained during the depressurization isapproximated as the systolic blood pressure, and a point where thepressure pulse wave amplitude suddenly becomes small is approximated asthe diastolic blood pressure. Various algorithms have been reviewed todetect such points.

For example, as shown in FIG. 9 and the following [Equation 1], a valueobtained by multiplying a predetermined ratio (first constant α, secondconstant β) set in advance to a maximum value of the pressure pulse waveamplitude is set as a blood pressure calculation parameter, and a cuffpressure at which the pressure pulse wave amplitude that matches (or isclosest to) the relevant parameter is obtained and is calculated as theblood pressure value (see Patent Document 1).

Systolic blood pressure calculation parameter=maximum value of pressurepulse wave amplitude×α

Diastolic blood pressure calculation parameter=maximum value of pressurepulse wave amplitude×β  [Equation 1]

Patent Document 1: Japanese Unexamined Patent Publication No. 3-81375

SUMMARY OF INVENTION

However, there is no theoretical evidence that the point where thepressure pulse wave amplitude suddenly changes matches the systolicblood pressure and the diastolic blood pressure. Thus, the first andsecond constants (α, β) for determining the blood pressure calculationparameter had to be experimentally or statistically determined based ona change pattern (hereinafter referred to as “envelope curve”) of agreat number of blood pressure values and pressure pulse waveamplitudes. Conventionally, the first constant α is a fixed value ofabout 0.5, and the second constant β is a fixed value of about 0.7,regardless of a state of a user and/or a state of a cuff at the time ofthe blood pressure measurement.

With respect to a pressure pulse wave that forms the envelope curve, thepressure pulse wave amplitude is obtained by detecting a volume changeof an artery transmitted to the cuff attached to the measurement site asa pressure change. The pressure pulse wave amplitude is thus subjectedto the influence of the properties of the cuff. One of the properties ofthe cuff is an air flow rate (hereinafter referred to as cuffcompliance) necessary for changing the pressure in the cuff (hereinafterreferred to as cuff pressure) by 1 mmHg as shown in the graph of FIG.10. As shown in FIG. 10, the cuff compliance becomes smaller as the cuffpressure becomes higher. Therefore, if a constant pulse wave amplitudeis provided to the cuff without depending on the cuff pressure, theamplitude is detected large as the cuff pressure becomes higher, asshown in FIG. 11.

For example, when measuring two users having different blood pressureswith a change in pressure pulse wave amplitude of the same envelopecurve shape, the pressure pulse wave amplitude, that is, the shape ofthe envelope curve detected by the sphygmomanometer, differs dependingon the blood pressure. Thus, there is difference in measurement accuracydepending on the blood pressure.

A state in which an artery B of an arm A of a user is compressed with acuff 2101 will be described with reference to FIG. 12. As shown in FIG.12, when the cuff pressure is pressurized to greater than or equal to apredetermined pressure of a blood pressure measurement range, thepressure of the central part of the cuff 2101 is sufficientlytransmitted to the artery B, so that the artery B is completely pressureclosed.

However, the artery B is not completely pressure closed because thepressure of the end of the cuff 2101 is not sufficiently transmitted tothe artery B. This depends on the structure of the cuff 2101, where theportion where the artery B is not pressure closed always forms in thegenerally used cuff structure. A blood flow exists at a portion wherethe artery is not pressure closed corresponding to the heart side of thecuff 2101, and hence, the volume change of the artery B occurs and thepressure pulse wave caused thereby is detected. In Patent Document 1,such a pressure pulse wave is referred to as the background pulse wave.Due to the existence of the background pulse wave, the systolic bloodpressure is detected in excess, and the diastolic blood pressure isdetected in underestimation in [Equation 1].

In a conventional art disclosed in Patent Document 1, [Equation 1] ischanged to the following [Equation 2]. An offset correction value (thirdconstant ζ) indicating the component of the background pulse wave isadded to the value obtained by multiplying a predetermined ratio (firstconstant α) set in advance to the maximum value of the pressure pulsewave amplitude to calculate the systolic blood pressure calculationparameter, and an offset correction value (fourth constant η) indicatingthe component of the background pulse wave is added to the valueobtained by multiplying a predetermined ratio (second constant β) set inadvance to the maximum value of the pressure pulse wave amplitude tocalculate the diastolic blood pressure calculation parameter.

Systolic blood pressure calculation parameter=maximum value of pressurepulse wave amplitude×α+ζ

Diastolic blood pressure calculation parameter=maximum value of pressurepulse wave amplitude×β+η  [Equation 2]

[Equation 2] is based on the presumption that the background pulse waveis constant without depending on the state of the user and/or the stateof the cuff 2101 at the time of the blood pressure measurement such asthe attribute of the user (peripheral length, blood pressure of the armA), the size or the cuff pressure of the cuff 2101, and the like.

However, it is recognized that the background pulse wave changes byvarious states at the time of the blood pressure measurement. Forexample, if the cuff pressure is raised, a width in which the artery Bis pressure closed becomes wider as shown in FIG. 12. Accompaniedtherewith, a width in which the background pulse wave generates becomesnarrow if the artery B is not pressure closed, whereby the level of thebackground pulse wave detected as a result becomes small, as shown inthe graph of FIG. 13.

The pressure pulse wave amplitude changes depending on the dynamicalproperties (arterial volume change involved in the arterial inner-outerpressure difference) of the artery B of the user. For example, a personwith soft artery B has a large amplitude thereof, whereas a person withadvanced arterial sclerosis has a small amplitude thereof (see FIG. 14).Therefore, the background pulse wave also changes depending on thedynamical properties.

If the systolic blood pressure and the diastolic blood pressure aredetermined by [Equation 2] in which the component of the backgroundpulse wave is defined as constant, the blood pressure is determined inunderestimation or in excess depending on the user.

Therefore, one or more embodiments of the present invention provides anelectronic sphygmomanometer and a blood pressure measuring method forcorrecting a constant based on measurement state related informationwhen executing a predetermined operation using the constant set inadvance with respect to change in a pressure pulse wave amplitudeindicating the volume change of the artery at the time of the bloodpressure measurement to accurately acquire the blood pressure valueusing the acquired data, thereby enhancing the satisfaction level of theuser.

According to one or more embodiments of the present invention, anelectronic sphygmomanometer includes a cuff to be attached to a bloodpressure measurement site, pressurization and depressurization means foradjusting a pressure to apply on the cuff, pressure detection means fordetecting a pressure in the cuff, blood pressure calculation means forcalculating a blood pressure value from a cuff pressure, recording meansfor recording the blood pressure value, and operation means forperforming an operation such as blood pressure measurement; wherein theblood pressure calculation means has a configuration adapted tocalculate a blood pressure calculation parameter based on apredetermined calculation of multiplying a constant with respect to amaximum value of a pressure pulse wave amplitude indicating volumechange of an artery at the time of blood pressure measurement; theelectronic sphygmomanometer further includes information acquiring meansfor separately acquiring measurement state related information relatedto a state of a user and/or a state of the cuff at the time of bloodpressure measurement, and correction means for correcting the bloodpressure calculation parameter by correcting the constant based on themeasurement state related information when the measurement state relatedinformation is acquired by the information acquiring means; theinformation acquiring means has a configuration adapted to acquireinformation of temporarily determined blood pressure value as themeasurement state related information related to the state of the user;and the correction means has a configuration adapted to correct thefirst and second constants based on the temporarily determined bloodpressure value.

According to one or more embodiments of the present invention, themeasurement state related information related to the state of the usermay include information related to the blood pressure value of the userat the time of the measurement, maximum value of the pressure pulse waveamplitude, information related to the measurement site, diseaseinformation of the user, and age information of the user.

According to one or more embodiments of the present invention, themeasurement state related information related to the state of the cuffmay include in addition to the information of the maximum value of thecuff pressure at the time of the blood pressure measurement and thewrapping strength of the cuff, cuff specification information such as asize and a type of the cuff.

According to one or more embodiments of the present invention, anoptimum blood pressure calculation parameter can be set for every stateof the user and/or the state of the cuff at the time of the bloodpressure measurement, and the measurement error can be reduced.

The temporarily determined blood pressure value can be temporarilydetermined during depressurization by a standard blood pressurecalculation parameter.

The temporarily determined blood pressure value can be temporarilydetermined during pressurization by a standard blood pressurecalculation parameter.

The temporarily determined blood pressure value can be the bloodpressure value recorded in the recording means.

According to one or more embodiments of the present invention, theoptimum blood pressure calculation parameter can be set for every bloodpressure value of the user, and the measurement error can be reduced.

According to one or more embodiments of the present invention, the bloodpressure calculation means has a configuration adapted to calculate asystolic blood pressure calculation parameter based on a predeterminedcalculation of multiplying a first constant to a maximum value of thepressure pulse wave amplitude, and adding a third constant related to acomponent of a background pulse wave generated when the pressure of thecuff is pressurized to a predetermined pressure outside a blood pressurevalue measurement range, and calculate a diastolic blood pressurecalculation parameter based on a predetermined calculation ofmultiplying a second constant to the maximum value of the pressure pulsewave amplitude and adding a fourth constant related to a component ofthe background pulse wave; and the correction means corrects the thirdand fourth constants based on the measurement state related information.

According to one or more embodiments of the present invention, the thirdand fourth constants related to the component of the background pulsewave can be corrected for every state of the user and/or the state ofthe cuff at the time of the blood pressure measurement, so that anaccurate blood pressure value can be calculated while suppressing theinfluence of error caused by the component of the background pulse wave.

According to one or more embodiments of the present invention, theinformation acquiring means may have a configuration adapted to acquireinformation of a temporarily determined blood pressure value as themeasurement state related information related to the state of the user;and the correction means may have a configuration adapted to correct thefirst and second constants or the third and fourth constants based onthe temporarily determined blood pressure value.

According to one or more embodiments of the present invention, theinformation acquiring means may have a configuration adapted to acquireinformation of a maximum value of the cuff pressure as the measurementstate related information; and the correction means may have aconfiguration adapted to correct the first and second constants or thethird and fourth constants based on the maximum value of the cuffpressure.

According to one or more embodiments of the present invention, theinformation acquiring means may have a configuration adapted to acquireinformation of a maximum value of the pressure pulse wave amplitude asthe measurement state related information related to the state of theuser; and the correction means may have a configuration adapted tocorrect the third and fourth constants based on the maximum value of thepressure pulse wave amplitude.

According to one or more embodiments of the present invention, theinformation acquiring means may have a configuration adapted to acquireinformation of a wrapping strength of the cuff as the measurement staterelated information; and the correction means may have a configurationadapted to correct the third and fourth constants based on theinformation of the wrapping strength of the cuff.

According to one or more embodiments of the present invention, theinformation acquiring means may have a configuration adapted to acquirecuff specification information related to a size and/or a type of thecuff as the measurement state related information; and the correctionmeans may have a configuration adapted to correct the third and fourthconstants based on the cuff specification information.

According to one or more embodiments of the present invention, theinformation acquiring means may have a configuration adapted to acquireinformation related to a measurement site of the user as the measurementstate related information; and the correction means may have aconfiguration adapted to correct the third and fourth constants based onthe information related to the measurement site of the user.

The information related to the measurement site of the user may includeinformation such as peripheral length and quality of the measurementsite.

The quality of the measurement site may include body fat percentage,subcutaneous fat percentage, or BMI.

According to one or more embodiments of the present invention, theinformation acquiring means may have a configuration adapted to acquiredisease information of the user as the measurement state relatedinformation; and the correction means may have a configuration adaptedto correct the third and fourth constants based on the diseaseinformation of the user.

According to one or more embodiments of the present invention, theinformation acquiring means may have a configuration adapted to acquireage information of the user as the measurement state relatedinformation; and the correction means may have a configuration adaptedto correct the third and fourth constants based on the age informationof the user.

According to one or more embodiments of the present invention, theinformation acquiring means may have a configuration adapted to acquirethe measurement state related information based on detection of changein an inner pressure of the cuff.

According to one or more embodiments of the present invention, inputmeans for permitting input of the measurement state related informationby the user may be further arranged; wherein the information acquiringmeans may have a configuration adapted to acquire the measurement staterelated information inputted before the start of the blood pressuremeasurement.

One or more embodiments of the present invention relates to a bloodpressure measurement method for adjusting a pressure to apply on a cuffwhen the cuff is attached to a blood pressure measurement site withpressurization and depressurization means, and calculating a bloodpressure value with blood pressure calculation means based on the cuffpressure detected by pressure detection means; the method may includethe steps of calculating a blood pressure calculation parameter byexecuting a predetermined calculation using a constant set in advancewith respect to a maximum value of a pressure pulse wave amplitudeindicating volume change of an artery at the time of blood pressuremeasurement in the blood pressure calculation means; separatelyacquiring measurement state related information related to a state of auser and/or a state of the cuff at the time of blood pressuremeasurement with information acquiring means; and correcting the bloodpressure calculation parameter by correcting the constant withcorrection means based on the measurement state related information whenthe measurement state related information is acquired by the informationacquiring means, wherein the step of calculating the blood pressurecalculation parameter by the blood pressure calculation means includescalculating the blood pressure calculation parameter based on apredetermined calculation of multiplying the constant to the maximumvalue of the pressure pulse wave amplitude, and the step of correctingby the correction means includes acquiring information of temporarilydetermined blood pressure value as the measurement state relatedinformation related to the state of the user by the informationacquiring means, and correcting the constant based on the temporarilydetermined blood pressure value.

According to one or more embodiments of the present invention, theoptimum blood pressure calculation parameter can be set for every stateof the user and/or the state of the cuff at the time of the bloodpressure measurement, and the measurement error can be reduced.

Moreover, according to one or more embodiments of the present invention,the optimum blood pressure calculation parameter can be set for everyblood pressure value of the user, and the process of reducing themeasurement error can be executed.

According to one or more embodiments of the present invention, the stepof calculating the blood pressure calculation parameter by the bloodpressure calculation means may include calculating a systolic bloodpressure calculation parameter based on a predetermined calculation ofmultiplying a first constant to a maximum value of the pressure pulsewave amplitude and adding a third constant related to a component of abackground pulse wave, and calculating a diastolic blood pressurecalculation parameter based on a predetermined calculation ofmultiplying a second constant to the maximum value of the pressure pulsewave amplitude and adding a fourth constant related to a component ofthe background pulse wave; and the step of correcting by the correctionmeans may include correcting the third and fourth constants based on themeasurement state related information.

According to one or more embodiments of the present invention, the thirdand fourth constants related to the component of the background pulsewave can be corrected for every state of the user and/or the state ofthe cuff at the time of the blood pressure measurement, so that aprocess of calculating an accurate blood pressure value can be executedwhile suppressing the influence of error caused by the component of thebackground pulse wave.

According to one or more embodiments of the present invention, theelectronic sphygmomanometer and the blood pressure measuring method foraccurately acquiring the blood pressure value using the acquired dataare provided, so that the satisfaction level of the user can beenhanced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a configuration of an electronicsphygmomanometer of a first embodiment.

FIG. 2 is a flowchart showing a blood pressure measurement operationaccording to the first embodiment.

FIG. 3 is a table showing a ratio for determining blood pressurecalculation parameters for standard and for every temporary averageblood pressure value.

FIG. 4 is a flowchart showing another example of the blood pressuremeasurement operation according to the first embodiment.

FIG. 5 is a flowchart showing another example of the blood pressuremeasurement operation according to the first embodiment.

FIG. 6 is a flowchart showing a blood pressure measurement operationaccording to a second embodiment.

FIG. 7 is a view showing a state when an artery of an arm of a user iscompressed with a cuff, and is a view describing a relationship betweena background pulse wave and a peripheral length of a measurement site ofthe user.

FIG. 8 is a view showing a state when an artery of an arm of the user iscompressed with the cuff, and is a view describing the relationshipbetween the background pulse wave and the size of the cuff.

FIG. 9 is a graph describing a blood pressure calculation algorithmexample of an oscillometric type sphygmomanometer.

FIG. 10 is a graph showing an example of a property (cuff compliance) ofthe cuff.

FIG. 11 is a graph showing an example of a pressure pulse wave amplitudedetected by the sphygmomanometer when a constant pulse wave amplitude isinputted.

FIG. 12 is a view showing a state when the artery of the arm of the useris compressed with the cuff, and is a view describing the relationshipbetween the background pulse wave and the blood pressure value.

FIG. 13 is a graph showing properties of the background pulse waveamplitude.

FIG. 14 is a graph showing an example of dynamic properties of theartery.

DETAILED DESCRIPTION OF INVENTION

Embodiments of the present invention will be described below withreference to the drawings.

First Embodiment

First, a first embodiment in which a blood pressure calculationparameter is optimized for every blood pressure value of a user will bedescribed.

As shown in FIG. 1, an electronic sphygmomanometer 2100 of a firstembodiment includes a cuff 2101, an air tube 2102, a pressure sensor2103, a pump 2104, a valve 2105, an oscillation circuit 2111, a pumpdrive circuit 2112, a valve drive circuit 2113, a timing unit 2115, apower supply 2116, a CPU 2120, a display unit 2121, a memory (forprocessing) 2122, a memory (for recording) 2123, an operation unit 2130,an interface 2171, and an external memory 2172.

FIG. 1 is a block diagram showing a configuration of the electronicsphygmomanometer 2100 of the first embodiment.

The cuff 2101 is a band shaped member that is connected to the air tube2102 and that is attached to a blood pressure measurement site of theuser to pressurize by air pressure.

The pressure sensor 2103 is an electrostatic capacitance type pressuresensor, in which a capacitance value changes according to the pressurein the cuff (cuff pressure).

The pump 2104 and the valve 2105 apply pressure to the cuff and adjust(control) the pressure in the cuff.

The oscillation circuit 2111 outputs a signal of the frequencycorresponding to the capacitance value of the pressure sensor 2103.

The pump drive circuit 2112 and the valve drive circuit 2113 drive thepump 2104 and the valve 2105, respectively.

The timing unit 2115 is a device for timing the current date and time,and transmitting the timed date and time to the CPU 2120 as necessary.

The power supply 2116 supplies power to each configuring unit.

The CPU 2120 executes the control of the pump 2104, the valve 2105, thedisplay unit 2121, the memories 2122, 2123, the operation unit 2130, andthe interface 2171, the blood pressure determination process and themanagement of the recording values.

The display unit 2121 is configured by a display device such as a liquidcrystal screen, and displays the blood pressure value according to asignal transmitted from the CPU 2120.

The memory (for processing) 2122 stores a ratio (to be described later)for determining blood pressure calculation parameter and a controlprogram of the sphygmomanometer.

The memory (for recording) 2123 stores the blood pressure value, andstores the date and time, the user, and the measurement values inassociation to each other as necessary.

The operation unit 2130 is configured by a power supply switch 2131, ameasurement switch 2132, a stop switch 2133, a record call out switch2141, and a user selection switch 2142, and permits the operation inputsuch as power ON/OFF of the sphygmomanometer and start of themeasurement, and transmits the inputted input signal to the CPU 2120.

The interface 2171 records/reads out the blood pressure to and from theexternal memory 2171 according to the control of the CPU 2120.

The blood pressure measurement operation using the electronicsphygmomanometer 2100 configured as above will be described according tothe flowchart of FIG. 2.

FIG. 2 is a flowchart showing the blood pressure measurement operationin the first embodiment.

First, when the power supply is turned ON by the operation of the powersupply switch 2131 (power supply SW) (step S2101), the CPU 2120 executesthe initialization process of the operation memory of thesphygmomanometer and performs the 0 mmHg adjustment of the pressuresensor 2103 (step S2102).

After the initialization process is finished, the cuff 2101 is wrappedaround the measurement site of the user, the user is selected (stepS2103) and the measurement switch 2132 (measurement SW) is pushed (stepS2104), so that the CPU 2120 pressurizes the cuff pressure up to apredetermined pressure by the pump 2104 (step S2105 to step S2106), andgradually depressurizes the cuff pressure by the valve 2105 (stepS2107).

The CPU 2120 extracts the pressure change component involved in thevolume change of the artery superimposed on the cuff pressure obtainedduring the depressurization, and calculates a temporary blood pressurevalue by a predetermined calculation (step S2108). After the temporaryblood pressure value is calculated (step S2109), the CPU 2120 opens thevalve 2105 and exhausts the air of the cuff. The CPU 2120 optimizes theblood pressure calculation parameter by the calculated temporary bloodpressure value (step S2110), and calculates the blood pressure valueusing the optimized blood pressure calculation parameter (step S2111).The CPU 2120 displays the calculated blood pressure value on the displayunit 2121 (step S2112), and records the same in the memory (forrecording) 2123 in association with the measurement date and time, andthe user (step S2113).

The process from step S2105 to step S2111 will be specifically describedcentering on the optimization process (step S2110) of the blood pressurecalculation parameter.

As shown in the table of FIG. 3, the memory (for processing) 2122records ratios α, β for determining blood pressure calculation parameter(systolic blood pressure calculation parameter, and diastolic bloodpressure calculation parameter) for standard and for every temporaryblood pressure value.

FIG. 3 is a table showing the ratios (α, β) for determining bloodpressure calculation parameters classified according to the standard andtemporary average blood pressure values.

The CPU 2120 for executing step S2108 in FIG. 2 calculates the temporarysystolic blood pressure calculation parameter and the temporarydiastolic blood pressure calculation parameter by multiplying the ratiosα, β (first and second constants) for determining standard bloodpressure calculation parameter to the maximum value of the pressurepulse wave amplitude, thereby calculating the temporary blood pressurevalue (temporary diastolic blood pressure, temporary systolic bloodpressure). The ratio α (first constant) for determining temporarysystolic blood pressure calculation parameter is set to 0.5 (50%), andthe ratio β (second constant) for determining temporary diastolic bloodpressure calculation parameter is set to 0.7 (70%). After the temporarysystolic blood pressure calculation parameter and the temporarydiastolic blood pressure calculation parameter are calculated, the CPU2120 calculates the temporary average blood pressure value with thefollowing equation.

Temporary average blood pressure value=temporary diastolic bloodpressure+(temporary systolic blood pressure−temporary diastolic bloodpressure)/3   [Equation 3]

After executing steps S2109 to S2110, the CPU 2120 determines the ratiosα, β for determining blood pressure calculation parameters correspondingto the temporary average blood pressure value based on FIG. 3,determines the blood pressure calculation parameter obtained bymultiplying the ratios α, β to the maximum value of the pressure pulsewave amplitude as the optimized blood pressure calculation parameter,and uses the optimized blood pressure calculation parameter to againcarry out the blood pressure calculation in step S2111.

In the present embodiment, the temporary average blood pressure value isdivided into a plurality of (e.g., three) sections for everypredetermined range, where the ratio α for determining systolic bloodpressure calculation parameter and the ratio β for determining diastolicblood pressure calculation parameter are set in advance for eachsection.

For the ratio α, the section smaller than 100 mmHg is the largest or55%, and the ratio α becomes smaller as the temporary average bloodpressure value becomes greater. For example, it is the smallest or 45%in the section of greater than or equal to 150 mmHg.

For the ratio β, on the other hand, the section of the section smallerthan 100 mmHg is the smallest or 60%, and the ratio β becomes greater asthe temporary average blood pressure value becomes greater. For example,it is the largest or 80% in the section of greater than or equal to 150mmHg.

As described above, the ratios α,β are classified based on the temporaryaverage blood pressure value, but may be classified based on any of thetemporary systolic blood pressure value and the temporary diastolicblood pressure value, or two or more of the plurality of blood pressurevalues.

Furthermore, the ratios may be classified with the cuff pressure atwhich the pulse wave amplitude becomes a maximum value.

Moreover, the blood pressure calculation parameter may be calculatedwith the following equation using any of the temporary systolic bloodpressure, the temporary diastolic blood pressure, temporary averageblood pressure, and the cuff pressure at which to become the maximumvalue of the pulse wave amplitude.

Systolic blood pressure calculation parameter P_SBP=Ψ×P ² +ω×P+ε

Diastolic blood pressure calculation parameter P_DBP=δ×P ²+π×P+ρ  [Equation 4]

Here, P indicates any of the temporary systolic blood pressure, thetemporary diastolic blood pressure, temporary average blood pressure, orthe cuff pressure at which to become the maximum value of the pulse waveamplitude, and Ψ, ω, ε, δ, π, ρ each indicate a predeterminedcoefficient determined by the cuff compliance.

An embodiment in which the temporarily determined blood pressure valueis temporarily determined during pressurization by the standard bloodpressure calculation parameter will be described according to aflowchart of FIG. 4 as another example of the blood pressure measurementoperation.

FIG. 4 is a flowchart showing one example of the blood pressuremeasurement operation in the first embodiment. In each embodimentdescribed below, the calculation in the CPU 2120 mainly differs, but thehardware configuration of the electronic sphygmomanometer 2100 issubstantially similar to the embodiment described above, and hence, theconfiguration of each unit will be described using the referencenumerals of FIG. 1.

First, when the power supply switch 2131 of the sphygmomanometer ispushed (step S2121), the CPU 2120 initializes the operation memory ofthe sphygmomanometer, and carries out 0 mmHg adjustment of the pressuresensor 2103 (step S2122).

The user whose blood pressure is to be measured is then selected (stepS2123), and the measurement switch 2132 is pushed (step S2124), so thatthe CPU 2120 gradually pressurizes the cuff pressure with the pump 2104(step S2125). The CPU 2120 extracts the pressure change componentinvolved in the volume change of the artery superimposed on the cuffpressure obtained during pressurization, and calculates the temporaryblood pressure value through a predetermined calculation (step S2126).After pressurizing up to a predetermined pressure (step S2127), the CPU2120 optimizes the blood pressure calculation parameter with thetemporary blood pressure value calculated during pressurization (stepS2128).

The CPU 2120 then gradually depressurizes the cuff pressure with thevalve 2105 (step S2129). The CPU 2120 extracts the pressure changecomponent involved in the volume change of the artery superimposed onthe cuff pressure obtained during depressurization, and calculates theblood pressure value through a predetermined calculation using theoptimized blood pressure calculation parameter (step S2130). Aftercalculating the blood pressure value (step S2131), the CPU 2120 opensthe valve 2105 to exhaust the air in the cuff. The CPU 2120 displays thecalculated blood pressure value on the display unit 2121 (step S2132),and records the same in the memory (for recording) 2123 in associationwith the measurement date and time and the user (step S2133).

The optimization process of the blood pressure calculation parameter isthe process similar to the process described above, and thus, thedescription thereof will not be given.

An embodiment in which the temporarily determined blood pressure valueis the blood pressure value recorded in the memory (for recording) 2123will now be described according to a flowchart of FIG. 5 as anotherexample of the blood pressure measurement operation.

FIG. 5 is a flowchart showing one example of the blood pressuremeasurement operation in the first embodiment.

When the power supply switch 2131 of the sphygmomanometer is pushed(step S2141), the CPU 2120 initializes the operation memory of thesphygmomanometer, and carries out 0 mmHg adjustment of the pressuresensor 2103 (step S2142).

The user whose blood pressure is to be measured is then selected (stepS2143), and the measurement switch 2132 is pushed (step S2144), so thatthe CPU 2120 reads out the immediate recording value of the selecteduser from the memory (for recording) 2123 (step S2145), and optimizesthe blood pressure calculation parameter based on such a recording value(step S2146).

The CPU 2120 then gradually pressurizes the cuff pressure with the pump2104 (step S2147). After pressurizing up to a predetermined pressure(step S2148), the CPU 2120 gradually depressurizes the cuff pressurewith the valve 2105 (step S2149).

The CPU 2120 extracts the pressure change component involved in thevolume change of the artery superimposed on the cuff pressure obtainedduring depressurization, and calculates the blood pressure value througha predetermined calculation using the optimized blood pressurecalculation parameter (step S2150). After calculating the blood pressurevalue (step S2151: YES), the CPU 2120 opens the valve 2105 to exhaustthe air in the cuff. The CPU 2120 displays the calculated blood pressurevalue on the display unit 2121 (step S2152), and records the same in thememory (for recording) 2123 in association with the measurement date andtime and the user (step S2153).

The optimization process of the blood pressure calculation parameter isthe process similar to the process described above, and thus thedescription thereof will not be given.

The recording value used to optimize the blood pressure calculationparameter may be an average value or a representative value of two ormore immediate recording values.

The recording value may use a value recorded in an external recordingmedium (external memory 2172 such as USB memory) or a personal computer,or a server via the Internet.

As described above, according to one or more embodiments of the presentinvention, an electronic sphygmomanometer 2100 includes biologicalinformation acquiring means for measuring a blood pressure value,recording means (memory 2123) for recording the blood pressure value,means (memory 2122) for storing a ratio for determining blood pressurecalculation parameters and a control program of a sphygmomanometer,operation means (operation unit 2130) for carrying out operations suchas blood pressure measurement, correction means (CPU 2120) forcorrecting the blood pressure value acquired by the biologicalinformation acquiring means based on measurement state relatedinformation related to the state of the user and/or the state of thecuff 2101 at the time of the blood pressure measurement, and outputmeans (display unit 2121) for outputting the corrected information(blood pressure value) after the correction, the biological informationacquiring means including a cuff 2101 to be attached to a blood pressuremeasurement site, pressurization and depressurization means 2104, 2105for adjusting the pressure to apply on the cuff 2101, pressure detectionmeans (pressure sensor 2103) for detecting a pressure in the cuff, andblood pressure calculation means (CPU 2120) for calculating a bloodpressure value from the cuff pressure, wherein the blood pressurecalculation means (CPU 2120) is adapted to calculate the blood pressurecalculation parameter based on a predetermined calculation ofmultiplying a ratio α serving as a first constant and a ratio β servingas a second constant set in advance with respect to a maximum value(change) of a pressure pulse wave amplitude indicating a volume changeof an artery at the time of the blood pressure measurement; and includesinformation acquiring means (CPU 2120 for executing steps S2108, S2126,S2145) for acquiring information of the temporarily determined bloodpressure value for the measurement state related information of theuser; and the correction means (CPU 2120 for executing steps S2110,S2128, S2146) is adapted to correct the blood pressure calculationparameter by correcting the ratios α, β based on the temporarilydetermined blood pressure value.

According to the configuration described above, an optimum bloodpressure calculation parameter is set for every blood pressure value ofthe user, and the measurement error can be reduced.

Second Embodiment

A second embodiment in which an offset correction value (third andfourth constants) related to the component of the background pulse waveis corrected by a measurement state related information related to thestate of the user and/or the state of the cuff 2101 at the time of theblood pressure measurement to reduce the measurement error will bedescribed according to a flowchart of FIG. 6.

FIG. 6 is a flowchart showing one example of the blood pressuremeasurement operation in the second embodiment.

First, when the power supply switch 2131 of the sphygmomanometer ispushed (step S2161), the CPU 2120 initializes the operation memory ofthe sphygmomanometer, and carries out 0 mmHg adjustment of the pressuresensor 2103 (step S2162).

The user whose blood pressure is to be measured is then selected (stepS2163), and the measurement switch 2132 is pushed (step S2164), so thatthe CPU 2120 gradually pressurizes the cuff pressure with the pump 2104(step S2165 to step S2166), and gradually depressurizes the cuffpressure with the valve 2105 (step S2167).

The CPU 2120 extracts the pressure change component involved in thevolume change of the artery superimposed on the cuff pressure obtainedduring depressurization, and calculates the temporary systolic bloodpressure value and the temporary diastolic blood pressure value througha predetermined calculation shown in the following [Equation 5] (stepS2168).

T_AmpSys=maximum value of pressure pulse wave amplitude×α+ζtsys

T_AmpDia=maximum value of pressure pulse wave amplitude×β+ηtdia  [Equation 5]

Here, T_AmpSys in [Equation 5] is the temporary systolic blood pressurecalculation parameter, and T_AmpDia is the temporary diastolic bloodpressure calculation parameter. Furthermore, ζtsys and ηtdia are offsetcorrection values (third and fourth constants) related to the componentof the background pulse wave generated when the pressure in the cuff2101 is pressurized to a predetermined pressure outside the bloodpressure value measurement range, and are values determined throughexperiment in advance.

The CPU 2120 determines the cuff pressure at a point the T_AmpSyscalculated in step S2168 intersects the envelope curve shown in FIG. 9as the temporary systolic blood pressure value, and the cuff pressure ata point the T_AmpDia calculated in step S2168 intersects the envelopecurve shown in FIG. 9 as the temporary diastolic blood pressure value.

The CPU 2120 then corrects the offset correction value ζ (thirdconstant) and the offset correction value η (fourth constant) related tothe component of the background pulse wave in [Equation 5] with thetemporary systolic blood pressure value and the temporary diastolicblood pressure value determined in step S2168. As shown in FIG. 13, thecomponent of the background pulse wave becomes smaller as the cuffpressure becomes higher, so that the offset correction value iscorrected through a predetermined calculation shown in the following[Equation 6] (step S2169).

ζ=ζtsys+temporary systolic blood pressure value×θ

η=ηtdia+temporary diastolic blood pressure value×ι  [Equation 6]

Here, θ and ι in [Equation 6] are values determined through experimentin advance.

The CPU 2120 calculates the systolic blood pressure calculationparameter and the diastolic blood pressure calculation parameter througha predetermined calculation shown in the following [Equation 7] in whichζ, η corrected in step S2169 are replaced with ζtsys, ηtdia of [Equation5] and optimizes the same (step S2170).

Systolic blood pressure calculation parameter=maximum value of pressurepulse wave amplitude×α+ζ

Diastolic blood pressure calculation parameter=maximum value of pressurepulse wave amplitude×β+η  [Equation 7]

Similar to the case of the temporary systolic blood pressure value andthe temporary diastolic blood pressure value, the CPU 2120 determinesthe cuff pressure at a point the systolic blood pressure calculationparameter and the diastolic blood pressure calculation parametercalculated in step S2170 intersect the envelope curve as the systolicblood pressure value and the diastolic blood pressure value (stepS2171).

The CPU 2120 displays the calculated blood pressure value on the displayunit 2121 (step S2172), and records the same in the memory (forrecording) 2123 in association with the measurement date and time andthe user (step S2173).

As described above, according to one or more embodiments of the presentinvention, an electronic sphygmomanometer 2100 includes biologicalinformation acquiring means for measuring a blood pressure value,recording means (memory 2123) for recording the blood pressure value,means (memory 2122) for storing a control program of thesphygmomanometer, operation means (operation unit 2130) for performingoperations such as blood pressure measurement, correction means (CPU2120) for correcting the blood pressure value based on a component of abackground pulse wave generated when the pressure of a cuff 2101 ispressurized to a predetermined pressure outside a blood pressure valuemeasurement range, and output means (display unit 2121) for outputtingcorrected information (blood pressure value) after the correction, thebiological information acquiring means including a cuff 2101 to beattached to a blood pressure measurement site, pressurization anddepressurization means 2104, 2105 for adjusting pressure to apply on thecuff 2101, pressure detection means (pressure sensor 2103) for detectinga pressure in the cuff, and blood pressure calculation means (CPU 2120)for calculating the blood pressure value from the cuff pressure; whereinthe blood pressure calculation means (CPU 2120) is adapted to multiply aratio α serving as a first constant set in advance with respect to amaximum value (change) of a pressure pulse wave amplitude indicating avolume change of an artery at the time of the blood pressure measurementand calculate a systolic blood pressure calculation parameter based on apredetermined calculation of adding an offset correction value ζ servingas a third constant related to the component of the background pulsewave, and also multiply a ratio β serving as a second constant set inadvance with respect to a maximum value (change) of the pressure pulsewave amplitude and calculate a diastolic blood pressure calculationparameter based on a predetermined calculation of adding an offsetcorrection value η serving as a fourth constant related to the componentof the background pulse wave, and includes information acquiring means(CPU 2120 that executes step S2168) for acquiring information of atemporary systolic blood pressure value and a temporary diastolic bloodpressure value as measurement state related information related to thestate of the user at the time of the blood pressure measurement; and thecorrection means (CPU 2120 that executes step S2169) is adapted tocorrect the blood pressure calculation parameters by correcting theoffset correction values ζ, η of the blood pressure value based on theinformation of the temporary systolic blood pressure value and thetemporary diastolic blood pressure value.

According to one or more embodiments of the present invention, theoffset correction values ζ, η related to the component of the backgroundpulse wave can be corrected for every state (blood pressure value of theuser in the present embodiment) of the user at the time of the bloodpressure measurement, so that an accurate blood pressure value can becalculated while suppressing the influence of error caused by thecomponent of the background pulse wave.

In the above description, the offset correction values (third and fourthconstants) are determined by multiplying a predetermined ratio withrespect to the temporary systolic blood pressure value and the temporarydiastolic blood pressure value, but an offset correction valuedetermination (for determining third and fourth constants) tablecorresponding to the temporary systolic blood pressure value and thetemporary diastolic blood pressure value may be stored in the memory2123 of the electronic sphygmomanometer 2100, and the offset correctionvalues (third and fourth constants) may be read out from the table.

An embodiment of correcting the offset correction value based on themaximum value of the cuff pressure will now be described as anotherexample of the blood pressure measurement operation.

Generally, the determination method of the blood pressure value of anoscillometric method includes the following.

First, there is a method (hereinafter referred to as depressurizationmeasuring method) of determining the blood pressure value during thedepressurization of the cuff pressure, in which depressurizationmeasuring method, the cuff pressure is pressurized to a pressure higherthan a predetermined pressure, where a point the pressure pulse waveamplitude rapidly increases while the cuff pressure is graduallydepressurized is determined as the systolic blood pressure value, and apoint the pressure pulse wave rapidly decreases while the cuff pressureis further gradually depressurized is determined as the diastolic bloodpressure value.

There is also a method (hereinafter referred to as pressurizationmeasuring method) of determining the blood pressure value during thepressurization of the cuff 2101, in which pressurization measuringmethod, the cuff is gradually pressurized, and a point the pressurepulse wave amplitude rapidly increases in the process is determined asthe diastolic blood pressure value, and a point the pressure pulse waverapidly decreases while the cuff pressure is gradually depressurized isdetermined as the systolic blood pressure value.

In the case of the depressurization measuring method, the cuff pressureis pressurized to a pressure higher by a predetermined pressure (e.g.,30 mmHg) than the measurement range, where the pressure value thereof isdefined as a cuff pressure maximum value Pcmax in the presentembodiment. In the blood pressure measurement device of thepressurization measuring method, pressurization is carried out until thepressure pulse wave amplitude information necessary for determining thesystolic blood pressure value is detected while gradually pressurizingthe cuff pressure. After the systolic blood pressure value isdetermined, the pressurization is stopped, and the cuff pressure israpidly depressurized with the valve 2105, where the cuff pressureimmediately before the start of the depressurization is defined as acuff pressure maximum value Pcmax in the present embodiment.

In the present embodiment, the CPU 2120 corrects the offset correctionvalues ζ, η indicating the component of the background pulse wavethrough a predetermined calculation shown in the following [Equation 8]based on the Pcmax. In the present embodiment, the offset correctionvalues ζ, η are corrected using the offset correction values ζtsys,ηtdia shown in [Equation 5], as shown in the following [Equation 8].

ζ=ζtsys+Pcmax×κ

η=ηtdia+Pcmax×λ  [Equation 8]

Here, κ and λ in [Equation 8] are values determined through experimentin advance. In the present embodiment, the offset correction values ζ, ηcorrected with [Equation 8] are applied to [Equation 7], similar to theembodiment shown in FIG. 6, to calculate and optimize the systolic bloodpressure calculation parameter and the diastolic blood pressurecalculation parameter thereby determining the blood pressure value.

In the present embodiment, the offset correction value determination(third and fourth constant determination) table in which the offsetcorrection value and the Pcmax are corresponded may be recorded inadvance in the memory 2123 of the electronic sphygmomanometer 2100, andthe offset correction values (third and fourth constants) may be readout from the table.

Therefore, an accurate blood pressure value can be calculated whilesuppressing the influence of the error caused by the difference in themaximum value Pcmax of the cuff pressure by correcting the offsetcorrection values ζ, η based on the information of the maximum valuePcmax of the cuff pressure.

An embodiment of correcting the offset correction value based on themaximum value of the pressure pulse wave amplitude will now be describedas another example of the blood pressure measurement operation.

In the present embodiment, the cuff pressure at a point the pressurepulse wave amplitude becomes a maximum (AmpMax) is defined as Pcamp inthe envelope curve shown in FIG. 9. The CPU 2120 corrects the offsetcorrection values ζ, η indicating the component of the background pulsewave according to a predetermined calculation shown in the following[Equation 9] based on the Pcamp.

ζ=ζtsys+Pcamp×μ

η=ηtdia+Pcamp×ν  [Equation 9]

Here, μ and ν in [Equation 9] are values determined through experimentsin advance. The optimization process of the blood pressure calculationparameter herein is the process similar to the process described above,and thus the description thereof will not be given.

In the present embodiment, the offset correction value determination(third and fourth constant determination) table in which the offsetcorrection value and the Pcamp are corresponded may be recorded inadvance in the memory 2123 of the electronic sphygmomanometer 2100, andthe offset correction values may be read out from the table.

Therefore, an accurate blood pressure value can be calculated whilesuppressing the influence of the error caused by the difference in themaximum value of the pressure pulse wave amplitude by correcting theoffset correction values ζ, η based on the information of the Pcamp orthe cuff pressure at the point the pressure pulse wave amplitude becomesa maximum (AmpMax).

Next, an embodiment of correcting the offset correction values based onthe wrapping strength of the cuff 2101 will be described as anotherexample of the blood pressure measurement operation.

In the case of the electronic sphygmomanometer 2100, as compared to thecase when the cuff 2101 is appropriately wrapped around the measurementsite such as the arm A (see FIG. 12) so as not to form a space, a greatamount of air needs to be flowed into the air bladder in the cuff 2101to apply the same pressure to the measurement site when a space isformed between the measurement site and the cuff 2101.

As described above, the pressure pulse wave amplitude detects the volumechange of the cuff 2101 that occurs with the volume change of the arteryB (see FIG. 12) as the pressure change, and hence the pressure pulsewave amplitude changes by the air volume in the cuff 2101, even if it isthe volume change of the same artery, where the pressure pulse waveamplitude becomes smaller the greater the air volume. Therefore, thecomponent of the background pulse wave changes according to the wrappingstrength of the cuff 2101.

The offset correction values of [Equation 7] thus need to be correctedbased on the wrapping strength of the cuff 2101. In the presentembodiment, the CPU 2120 calculates the systolic blood pressurecalculation parameter and the diastolic blood pressure calculationparameter through a predetermined calculation shown in the following[Equation 10] in which the correction by the manner of wrapping the cuff2101 is added to [Equation 7], and optimizes the same. In other words,in the present embodiment, a predetermined ratio ξ is multiplied to theoffset correction value ζ to correct the same, and a predetermined ratioσ is multiplied to the offset correction value η to correct the same.

Systolic blood pressure calculation parameter=maximum value of pressurepulse wave amplitude×α+ζ×ξ

Diastolic blood pressure calculation parameter=maximum value of pressurepulse wave amplitude×β+η×σ  [Equation 10]

Here, ξ and σ in [Equation 10] are values determined through experimentsin advance. Such values may be determined through a method of recordingthe offset correction value determination (third and fourth constantcorrection) table in which the values are corresponded with the wrappingstrength of the cuff 2101 in the memory 2123 of the electronicsphygmomanometer 2100 in advance and reading out the values from thetable.

The wrapping strength of the cuff 2101 may be detected by the proportionof the change in cuff pressure when pressurizing the cuff 2101 using theknown technique described Japanese Unexamined Patent Publication No.62-84738, Japanese Unexamined Patent Publication No. 5-62538, andJapanese Patent No. 4134234.

Therefore, by correcting the offset correction values ζ, η based on theinformation of the wrapping strength of the cuff 2101, an accurate bloodpressure value can be calculated while suppressing the influence of theerror caused by the difference in air volume in the cuff 2101 thatoccurs from the difference in the wrapping strength.

An embodiment of correcting the offset correction values based onspecifications (size) of the cuff 2101 will now be described as anotherexample of the blood pressure measurement operation.

In the case of the electronic sphygmomanometer 2100, the attenuation ofthe pressure transmission to the artery B becomes greater the longer theperipheral length of the measurement site. Therefore, the cuff 2101 ofan appropriate size needs to be selected according to the peripherallength of the measurement site to carry out accurate blood pressuremeasurement. In other words, the width (direction orthogonal to theperipheral direction of the measurement site) and the length (peripheraldirection of the measurement site) of the cuff 2101 need to be longerthe longer the peripheral length of the measurement site. The width andthe length of the cuff suitable for the peripheral length of themeasurement site are advised/recommended in WHO (World HealthOrganization) or the like.

As the size (width, length) of the size 2101 becomes longer the longerthe peripheral length of the measurement site, the size of the airbladder in the cuff 2101 also becomes greater therewith. Therefore, thepressure pulse wave amplitude to be detected becomes smaller when thesize of the cuff 2101 becomes greater, so that the component of thebackground pulse wave also becomes smaller (see FIG. 7).

Therefore, the offset correction values of [Equation 7] need to becorrected with the size of the cuff 2101. In the present embodiment, theCPU 2120 calculates the systolic blood pressure calculation parameterand the diastolic blood pressure calculation parameter through apredetermined calculation shown in the following [Equation 11] in whichthe correction by the size of the cuff 2101 is added to [Equation 7],and optimizes the same. In other words, in the present embodiment, apredetermined ratio τ is multiplied to the offset correction value ζcorrect the same, and a predetermined ratio υ is multiplied to theoffset correction value η to correct the same.

Systolic blood pressure calculation parameter=maximum value of pressurepulse wave amplitude×α+ζ×τ

Diastolic blood pressure calculation parameter=maximum value of pressurepulse wave amplitude×β+η×υ  [Equation 11]

Here, τ and υ in [Equation 11] are values determined through experimentsin advance. Such values may be determined through a method of recordingthe offset correction value determination (third and fourth constantcorrection) table in which the values are corresponded with the size ofthe cuff 2101 in the memory 2123 of the electronic sphygmomanometer 2100in advance and reading out the values from the table.

Therefore, an accurate blood pressure value can be calculated whilesuppressing the influence of the error caused by the difference in sizeof the air bladder in the cuff 2101 by correcting the offset correctionvalues ζ, η based on the information of the size of the cuff 2101.

The size of the cuff 2101 may be inputted before the measurement with aswitch, the switch being arranged in the input unit such as theoperation unit 2130, or may be automatically detected by arranging asensor for detecting the size of the cuff 2101 at the connecting portionwith the cuff 2101 of the main body of the electronic sphygmomanometer2100.

By arranging a switch in the input unit such as the operation unit 2130,and enabling various types of information such as the size of the cuff2101 to be inputted before the measurement, various types of informationnecessary for the calculation of the blood pressure value can be easilyacquired in advance, and the time required for the blood pressuremeasurement can be shortened.

As the air volume to be flowed into the cuff 2101 until a predeterminedcuff pressure is reached becomes large in accordance with the increasein the size of the cuff 2101, the elapsed time thereof also becomeslonger. Therefore, the time until the predetermined cuff pressure isreached may be measured based on the change in the cuff pressure in oneblood pressure measurement, and the size of the cuff 2101 may bedetected based on such time.

Therefore, various types of information can be acquired with a simpleconfiguration without separately arranging the input unit, the sensor orthe like for inputting various types of information necessary for thecalculation of the blood pressure value such as the size of the cuff2101.

The case of correcting the offset correction values ζ, η based on theinformation related to the size of the cuff 2101 of the informationrelated to the specifications of the cuff 2101 has been described, butthe correction may also be carried out based on the information relatedto the type such as structure and material of the information related tothe specifications of the cuff 2101. For example, with respect to thecuff in which the structure of the air bladder in the cuff 2101 is asingle structure like a balloon and the cuff in which a gore structureis provided at the side surface of the air bladder as described inJapanese Patent No. 3747917, the volume of air to be flowed into the airbladder so that the cuff 2101 reaches the predetermined inner pressureis greater for the latter cuff. Furthermore, the volume of air to beflowed into the air bladder so that the cuff 2101 reaches thepredetermined inner pressure is greater the softer the material of theair bladder in the cuff 2101.

In contrast, by correcting the offset correction values ζ, η based onthe information related to the type of the cuff 2101, an accurate bloodpressure value can be calculated while suppressing the influence of theerror caused by the difference in the air volume by the type of the cuff2101.

As described above, the size of the cuff 2101 used for the measurementbecomes greater the longer the peripheral length of the measurementsite. Therefore, the offset correction values (third and fourthconstants) of [Equation 11] may be corrected by the peripheral length ofthe measurement site based on the fact that the component of thebackground pulse wave changes in accordance with the size of the cuff2101 as shown in FIG. 8. Thus, an accurate blood pressure value can becalculated while suppressing the influence of the error caused by thedifference in the size of the cuff 2101.

The expansion of the air bladder in the cuff 2101 becomes greater thesofter the quality of the measurement site. In this case, a state sameas the state in which there is a space between the measurement site andthe cuff 2101 is realized, and the pressure pulse wave amplitude becomessmall. Therefore, the correction may be carried out by the quality ofthe measurement site. An accurate blood pressure value thus can becalculated while suppressing the influence of the error caused by thedifference in the expansion of the air bladder of the cuff 2101.

In this case, the peripheral length or the quality of the measurementsite may be inputted from the input unit such as the operation unit2130, or the time until reaching the predetermined cuff pressure may bemeasured based on the change in the cuff pressure in one blood pressuremeasurement and the peripheral length or the quality may be detectedbased on such time. The input of the quality of the measurement site maybe substituted with BMI (Body Mass Index), body fat percentage, or thelike. For example, determination is made that a great amount of fatexists at the measurement site if the body fat percentage is large, andcorrection can be made assuming the quality of the measurement site issoft.

Therefore, the information related to the measurement site can beacquired with a simple configuration without separately arranging theinput unit, the sensor or the like for inputting various types ofinformation related to the measurement site.

An embodiment of correcting the offset correction values based on theuser information inputted before the start of the blood pressuremeasurement will now be described as another example of the bloodpressure measurement operation.

In the case of the electronic sphygmomanometer 2100, the shape of theenvelope curve shown in FIG. 9 is determined in accordance with thedynamical properties of the artery. FIG. 14 is a graph showing anexample of the dynamical properties of the artery, where one of thefactors for determining the dynamical properties of the artery as shownin FIG. 14 includes arterial elasticity. The elasticity of the arterydepends on the age and the disease (particularly arterial sclerosis),and the arterial elasticity becomes harder with aging and advancement indisease. When the arterial elasticity becomes hard, the artery is almostimpossible to be pressure closed even if it is compressed with the cuff2101, and thus, the background pulse wave exists until the cuff pressurebecomes high compared to a person with soft arterial elasticity.

The age and disease information are inputted in advance, and the offsetcorrection values ζ, η of [Equation 7] are corrected with the age anddisease information. In the present embodiment, the input of the age anddisease information is permitted with the input unit such as theoperation unit 2130, and the CPU 2120 calculates the systolic bloodpressure calculation parameter and the diastolic blood pressurecalculation parameter through a predetermined calculation shown in thefollowing [Equation 12] in which the correction based on the inputtedage and disease information is added to [Equation 7], and optimizes thesame. In other words, in the present embodiment, a predetermined ratio φis multiplied to the offset correction value ζ to correct the same, anda predetermined ratio χ is multiplied to the offset correction value ηto correct the same.

Systolic blood pressure calculation parameter=maximum value of pressurepulse wave amplitude×α+ζ×φ

Diastolic blood pressure calculation parameter=maximum value of pressurepulse wave amplitude×β+η×χ  [Equation 12]

Here, φ and χ in [Equation 12] are values determined through experimentsin advance. Such values may be determined through a method of recordingthe offset correction value determination table in which the values arecorresponded with the age and disease information in the memory 2123 ofthe electronic sphygmomanometer 2100 in advance and reading out thevalues from the table.

The age and disease information may be inputted by the operation unit2130 at the start of the measurement. The user and the age or diseaseinformation may be recorded in the memory 2123 in association with eachother, and the information may be read from the memory 2123 by selectingthe user by the operation unit 2130 at the start of the measurement. Theage and disease information may be recorded in a medium such as theexternal memory 2172, and the information may be read out at the startof the measurement.

In the case of the present embodiment, the time until reaching apredetermined cuff pressure is measured based on the change in the cuffpressure in one blood pressure measurement, the elasticity of the arteryB of the user is detected based on the time, and the disease information(in this case, information of arterial sclerosis) may be acquired basedon the detection result.

Therefore, an accurate blood pressure value can be calculated whilesuppressing the influence of the error caused by the difference inelasticity of the artery B by correcting the offset correction values ζ,η based on the age and disease information of the user.

Embodiments of the present invention are not limited only to theconfiguration of the above-described embodiments, and a great number ofembodiments can be realized.

For example, the electronic sphygmomanometer 2100 may be configured todownload an appropriate parameter, threshold value, algorithm, or thelike from a dedicated server to expand the function. In this case, theversion of the software may be upgraded with the hardware as is, oroptimization can be easily realized by the user himself/herself.

The function expansion of the electronic sphygmomanometer 2100 may beexecuted from a user terminal such as a personal computer possessed bythe user without using the server. In this case, the parameter, thethreshold value, the algorithm, and the like may be downloaded from arecording medium such as a CD-ROM.

The electronic sphygmomanometer 2100 may be directly and communicablyconnected wirelessly or by wire to other biological informationacquiring device such as a body composition meter, a pedometer, or anelectronic thermometer. In this case as well, data may be mutuallytransmitted and received to enhance the individual accuracy.

Embodiments of the present invention can be used in an electronicsphygmomanometer adopting an oscillometric method that uses a cuff.

While the invention has been described with respect to a limited numberof embodiments, those skilled in the art, having benefit of thisdisclosure, will appreciate that other embodiments can be devised whichdo not depart from the scope of the invention as disclosed herein.Accordingly, the scope of the invention should be limited only by theattached claims.

DESCRIPTION OF REFERENCE NUMERALS

-   2100 electronic sphygmomanometer-   2101 cuff-   2103 pressure sensor-   2104 pump-   2105 valve-   2120 CPU-   2121 display unit-   2122 memory (for processing)-   2123 memory (for recording)-   2130 operation unit

1. An electronic sphygmomanometer comprising: a cuff to be attached to ablood pressure measurement site; pressurization and depressurizationmeans for adjusting a pressure to apply on the cuff; pressure detectionmeans for detecting a pressure in the cuff; blood pressure calculationmeans for calculating a blood pressure value from a cuff pressure;recording means for recording the blood pressure value; and operationmeans for performing a blood pressure measurement; wherein the bloodpressure calculation means comprises a configuration that calculates ablood pressure calculation parameter based on a predeterminedcalculation of multiplying a constant with respect to a maximum value ofa pressure pulse wave amplitude indicating a volume change of an arteryat a time of blood pressure measurement, and wherein the electronicsphygmomanometer further comprises: information acquiring means forseparately acquiring measurement state related information related to astate of a user and/or a state of the cuff at the time of blood pressuremeasurement; and correction means for correcting the blood pressurecalculation parameter by correcting the constant based on themeasurement state related information when the measurement state relatedinformation is acquired by the information acquiring means, wherein theinformation acquiring means comprises a configuration that acquiresinformation of a temporarily determined blood pressure value as themeasurement state related information related to the state of the user,and wherein the correction means comprises a configuration that correctsthe constant based on the temporarily determined blood pressure value.2. The electronic sphygmomanometer according to claim 1, wherein theblood pressure calculation means comprises a configuration thatcalculates a systolic blood pressure calculation parameter based on apredetermined calculation of multiplying a first constant to a maximumvalue of the pressure pulse wave amplitude, and adding a third constantrelated to a component of a background pulse wave generated when thepressure of the cuff is pressurized to a predetermined pressure outsidea blood pressure value measurement range, wherein the blood pressurecalculation means comprises a configuration that calculates a diastolicblood pressure calculation parameter based on a predeterminedcalculation of multiplying a second constant to the maximum value of thepressure pulse wave amplitude and adding a fourth constant related to acomponent of the background pulse wave, and wherein the correction meanscorrects the third and fourth constants based on the measurement staterelated information.
 3. The electronic sphygmomanometer according toclaim 2, wherein the information acquiring means comprises aconfiguration that acquires information of a temporarily determinedblood pressure value as the measurement state related informationrelated to the state of the user, and wherein the correction meanscomprises a configuration that corrects the first and second constantsor the third and fourth constants based on the temporarily determinedblood pressure value.
 4. The electronic sphygmomanometer according toclaim 2, wherein the information acquiring means comprises aconfiguration that acquires information of a maximum value of the cuffpressure as the measurement state related information, and wherein thecorrection means comprises a configuration that corrects the first andsecond constants or the third and fourth constants based on the maximumvalue of the cuff pressure.
 5. The electronic sphygmomanometer accordingto claim 2, wherein the information acquiring means comprises aconfiguration that acquires information of a maximum value of thepressure pulse wave amplitude as the measurement state relatedinformation related to the state of the user, and wherein the correctionmeans comprises a configuration that corrects the first and secondconstants or the third and fourth constants based on the maximum valueof the pressure pulse wave amplitude.
 6. The electronic sphygmomanometeraccording to claim 2, wherein the information acquiring means comprisesa configuration that acquires information of a wrapping strength of thecuff as the measurement state related information, and wherein thecorrection means comprises a configuration that corrects the first andsecond constants or the third and fourth constants based on theinformation of the wrapping strength of the cuff.
 7. The electronicsphygmomanometer according to claim 2, wherein the information acquiringmeans comprises a configuration that acquires cuff specificationinformation related to a size and/or a type of the cuff as themeasurement state related information, and wherein the correction meanscomprises a configuration that corrects the first and second constantsor the third and fourth constants based on the cuff specificationinformation.
 8. The electronic sphygmomanometer according to claim 2,wherein the information acquiring means comprises a configuration thatacquires information related to a measurement site of the user as themeasurement state related information, and wherein the correction meanscomprises a configuration that corrects the first and second constantsor the third and fourth constants based on the information related tothe measurement site of the user.
 9. The electronic sphygmomanometeraccording to claim 2, wherein the information acquiring means comprisesa configuration that acquires disease information of the user as themeasurement state related information, and wherein the correction meanscomprises a configuration that corrects the first and second constantsor the third and fourth constants based on the disease information ofthe user.
 10. The electronic sphygmomanometer according to claim 2,wherein the information acquiring means comprises a configuration thatacquires age information of the user as the measurement state relatedinformation, and wherein the correction means comprises a configurationthat corrects the first and second constants or the third and fourthconstants based on the age information of the user.
 11. The electronicsphygmomanometer according to claim 2, wherein the information acquiringmeans comprises a configuration that acquires the measurement staterelated information based on a detection of a change in an innerpressure of the cuff.
 12. The electronic sphygmomanometer according toclaim 2, further comprising: input means for permitting input of themeasurement state related information by the user; wherein theinformation acquiring means comprises a configuration that acquires themeasurement state related information inputted before the start of theblood pressure measurement.
 13. A blood pressure measurement method foradjusting a pressure to apply on a cuff when the cuff is attached to ablood pressure measurement site with pressurization and depressurizationmeans, and calculating a blood pressure value with blood pressurecalculation means based on the cuff pressure detected by pressuredetection means, the method comprising the steps of: calculating a bloodpressure calculation parameter by executing a predetermined calculationusing a constant set in advance with respect to a maximum value of apressure pulse wave amplitude indicating a volume change of an artery ata time of blood pressure measurement in the blood pressure calculationmeans; separately acquiring measurement state related informationrelated to a state of a user and/or a state of the cuff at the time ofblood pressure measurement with information acquiring means; andcorrecting the blood pressure calculation parameter by correcting theconstant with correction means based on the measurement state relatedinformation when the measurement state related information is acquiredby the information acquiring means, wherein the step of calculating theblood pressure calculation parameter by the blood pressure calculationmeans comprises calculating the blood pressure calculation parameterbased on a predetermined calculation of multiplying the constant to themaximum value of the pressure pulse wave amplitude, and wherein the stepof correcting by the correction means comprises: acquiring informationof a temporarily determined blood pressure value as the measurementstate related information related to the state of the user by theinformation acquiring means; and correcting the constant based on thetemporarily determined blood pressure value.
 14. The blood pressuremeasurement method according to claim 13, wherein the step ofcalculating the blood pressure calculation parameter by the bloodpressure calculation means further comprises: calculating a systolicblood pressure calculation parameter based on a predeterminedcalculation of multiplying a first constant to a maximum value of thepressure pulse wave amplitude and adding a third constant related to acomponent of a background pulse wave; and calculating a diastolic bloodpressure calculation parameter based on a predetermined calculation ofmultiplying a second constant to the maximum value of the pressure pulsewave amplitude and adding a fourth constant related to a component ofthe background pulse wave, and wherein the step of correcting by thecorrection means comprises correcting the third and fourth constantsbased on the measurement state related information.